This invention relates to carburetor for an internal combustion engine and more particularly to a staged carburetor for use thereon.
Staged carburetors are installed on internal combustion engines in place of larger carburetors, i.e. carburetors with more barrels or air induction passages. Ideally, the performance characteristics of a staged carburetor approximates that of a conventional, non-staged carburetor which it replaces. Thus, for example, a staged two-barrel or staged dual carburetor performs approximately the same way as a non-staged four-barrel carburetor insofar as air capacity, fuel flow rates, etc. are concerned. In using a two-barrel staged carburetor, the engine manifold on which the carburetor is installed usually has two inlet ports, one of which is beneath each carburetor passage. It is important that the air-fuel mixture produced in the carburetor and discharged into the engine's intake manifold have a distribution pattern such that the mixture is evenly distributed to all engine cylinders. This increases engine efficiency and reduces engine emissions. Previous staged carburetor designs have not always provided an air-fuel mixture at the carburetor outlet by which even distribution to all engine cylinders is possible. For example, prior staged dual carburetor designs have typically required that one side of the carburetor be open initially and that the other side of the carburetor not open until a certain engine operating point, usually related to engine load, is reached. Consequently, the air-fuel mixture spilling out of these carburetors is discharged into an engine's intake manifold through only one of the two manifold intake ports. This results in an uneven fuel distribution pattern which reduces engine efficiency and increases emmissions.